Statement by Daniel Greenberger

Daniel Greenberger's " interview" notes:

On the 2005 March Meeting:

Our new Topical Group was authorized by the APS executive committee late last spring, but with some confusion over what we were entitled to do, we only got started to really operate last November (shortly before the sorters' meeting to set up invited talks). We were told we could have one session of invited talks, and with very little time left we managed to set up a very impressive group of speakers, with Tony Leggett as chairman, so that the session was well attended. The overall topic was progress in quantum information and quantum physics in general. Speakers were Michel Devoret, who talked on his work on constructing superconducting quantum bits (qubits) with Josephson Junctions. Dietrich Liebfried talked about the work of David Wineland's group on constructing quantum computers with an array of ion traps. Wojciech Zurek talked about his fundamental concept of “envariance.” Charles Bennett reviewed recent results on quantum channel capacities. Anton Zeilinger was scheduled to speak about his new experiments in realizing “one-way quantum computing,” an idea of Raussendorf and Briegel, using entangled “cluster states.” Unfortunately, he couldn't make it at the last minute and the talk was very ably given by his post-doc, Markus Aspelmeyer.

While setting up these talks we discovered with only two weeks to go before the deadline that we could also set up contributed sessions. We sent out a hurried call for papers and got enough replies that we were able to actually have six contributed sessions, two of which were focus sessions, since they included invited talks. There were three of these. Hideo Mabuchi talked about the interface of control theory with quantum information science, and the progress of his group at Caltech in such areas as quantum feedback control, quantum metrology, and quantum state preparation. Isaac Chuang of MIT gave an assessment of all the present methods of trying to attain a quantum computer, with particular attention to issues of fault tolerance. Ivan Deutsch gave a talk on the advantages of using ultracold trapped neutral atoms, which couple only weakly to the environment, for quantum computing, and described schemes for controlling their interactions. In all we managed to get over 60 contributed papers, and all the sessions were well attended. One of the focus groups was co-sponsored by both DAMOP (atoms and molecules) and DCOMP (computing). The titles of the contributed sessions were: quantum entanglement and entropy; quantum dots, gates, and single photon devices (focus session); quantum mechanical properties; pathway to practical quantum computing (focus session); quantum computing; and Josephson Junctions and Squids II.

Purpose of the Group

The impetus for forming the group came from the feeling that people who work on foundational problems in quantum theory have no natural home in APS. There is strong overlap with various groups, such as DAMOP, and DCOMP, and laser groups, but if you are discussing a fundamental problem in quantum theory and using a neutron interferometer to explore it, you don't really have a natural audience in neutron physics. If you are using laser techniques such as down-conversion, a method for producing two entangled photons, and using them to elucidate some point about Bell inequalities, you don't have a natural audience among laser scientists, or atomic physicists, etc. Similarly, although quantum cryptography and the fine points of information theory all use some kind of physical system to implement their ideas, only people interested in cryptography or information theory per se will be interested. And the same goes for quantum computing. You can use a system of trapped ions or neutral atoms, etc., to describe what you are doing, but if what you are interested in is error correction, only quantum computation people are interested, and not ion people or atom people. [HM: I think this is much less true now than it was a few years ago.]

Similarly, there are no APS prizes or awards that are available for people in the field. And the only way that they can usually be elected as fellows of the APS is to distinguish themselves in some other field. And there are other problems as well. Many young people are becoming interested in the field, but there are few opportunities for having their research funded in this field. Most granting programs set aside money for, say, optics, by which they mean developing new lasers, or materials, etc., but they don't usually consider fundamental problems. And from experience on such panels, I can tell you personally that the type of people chosen for such panels tend not to look favorably on such research. They would much rather see a payoff in instruments they can use, etc. The field needs an effective lobbying group to talk to such agencies as NSF.

History of the Field

Some problems in the field stem from its history. The struggles of Bohr and Einstein are well know in helping to develop quantum theory. And when Einstein, Podolsky, and Rosen (EPR) developed their famous "paradox", in 1935, they started a discussion that has extended down to this day. In fact, the EPR paper is still the most down-loaded paper from the APS archives, 80 years after it was written. You might think that that would give some life to the field. But the reaction was a rather special one. People thought that it was a discussion for old men, and that there was no way to experimentally test the difference between Bohr and Einstein, so it was a waste of time to bother joining the discussion. When I was a student in the late 50's, and I expressed interest in the discussion, I was told by an advisor that there is an old Chinese proverb that "when elephants fight, it's the grass that gets trampled," meaning I would be smart to let the giants fight it out among themselves, and to keep out of their way. On top of that is the old aversion to philosophical discussions that physicists seem to have bred into them at an early age, in spite of the fact that most of the great physicists had strong tendencies to philosophize. But all that is long past. In 1964 came Bell's theorem, which gave an idealized experiment that could tell the difference between the EPR and Bohr points of view, and by the early 70's, people had started to perform difficult but clever laboratory tests of quantum vs. classical correlations. This work has become progressively more beautiful, and has utilized all the latest laboratory techniques, and today is a sophisticated field at the forefront of physics. It has spun off the new and rising fields of quantum cryptography and quantum computing, and there is a growing appreciation of the field. And yet even today this appreciation is very spotty, and many people still think of it in terms that were more appropriate to the 50's. For example, while Physical Review Letters has a special section that deals in fundamental physics and quantum information, Physical Review A has often appeared to hold some editorial bias against papers written about “quantum foundations.”

The Group at Present

So clearly there is a lot of work for our group to do in educating our own peers, and funding agencies, as well as establishing contacts with the general public. We must also establish routes for publishing, and easing the route to career advancement for our younger members. Therefore the group hopes to reach out to everyone working in the area, and be as inclusive as we can. At the moment, one of our chief goals is to increase our membership as fast as we can, and then hold elections as soon as feasible. Until then, the group is being run by an ad-hoc committee of advisors set up by the organizers of the petition that started the group, Daniel Greenberger of CCNY in New York, and Anton Zeilinger of the University of Vienna. We first chose a small group, Tony Leggett, Paul Kwiat, and Jeff Kimble, to help suggest names of the invited speakers for the March meeting. Then we decided that we needed a dynamic, rising, and presentable young physicist to be chairman, and we chose Hideo Mabuchi of Caltech for that role. The three of us together chose the rest of the advisory board.